SU884117A1 - Signal demodulator - Google Patents

Description

(54) SIGNAL DEMODULATOR

I

The invention relates to radio electronics and can be used in devices of automation, remote control, measurement technology, and. etc. to get a DC output signal proportional to the frequency of the input signal.

A demodulating device is known comprising a clock, a synchronization circuit, an AND element, counters, a protection control circuit, a control trigger, a voltage converter — a pulse frequency, a smoothing filter. The disadvantage of this device is its narrow dynamic range. .. It is also known to have a demodulation device containing an input signal forwarder whose input is connected to input-. bus, and the output is connected to the first one at the trigger input, the filter, voltage to frequency converter, the input of which is connected to the filter input, and the output is connected to the second input, trigger 2J.

A disadvantage of the known device is also a narrow dynamic range.

Zoe.

The purpose of the invention is to expand the dynamic range.

The goal is achieved by the fact that the signal demodulator containing the input driver, the input of which is connected to the input bus and the output connected to the first trigger input, the filter converter is strained to the frequency whose input is connected to the input of the filter and the output connected to the second the trigger input, the first and second elements I, the element EQUIVALENCE, the inverter, the analog adder are entered, the inputs of the element EQUIVALENCE are connected to the trigger inputs, and the output is connected to the first inputs of the first n second element And the second inputs of which are connected respectively to the first and second outputs of the trigger, the output of the first element And connected to the first input of the analog adder, the second input of which through the inverter is connected to the output of the second element And, the output of the analog adder is connected to the input of the filter, whose output is connected to output bus.

Claims (2)

FIG. 1 shows a signal demodulator circuit; in fig. 2 - time diagrams normalized by amplitude, which explain his work; in fig. 3 normalized graphs of the amplitude of the first harmonic (ai) in the spectrum of the pulse sequence input to the filter, the magnitude of the modulating signal V for the known (a) and for the proposed demodulator (b). The device contains (input signal shaper 1, trigger, 2 filter 3, voltage to frequency converter 4, first 5 and second AND elements, EQUIVALENCE element 7, inverter 8, analog adder 9. The device operates as follows. Former I input enters the frequency-modulated signal, which is converted into a sequence of square frequency-modulated pulses, arriving at the first input of trigger 2 and the first input of element 7 EQUIVALENCE. The pulses from the direct output of trigger 2 arrive at the first input element 6 And, the second input of which receives pulses from the output of element 7 EQUIVALENCE.The pulses from the output of element And 6 arrive at the first input of the analog adder 9. Pulses from the inverse output of trigger 2 arrive at the first input of element 5, to the second input of which impulses from the output of the element .7 EQUIVALENCE. The pulses from the output of the element And 5 are inverted by the inverter 8 and received from the second analog of the analog adder 9. As a result, at the output of the analog adder 9, two-polar impulses are generated the input of the voltage converter 4 to the frequency that forms the demodulator feedback circuit and the input of the filter 3, which selects the useful component of the signal In the absence of the useful component in the input frequency-modulated signal, there are no pulses at the output of the analog adder 9. With a positive useful component, contained in the frequency-modulated signal, at the output of analog adder 9, positive polarity pulses appear, the duration of which is proportional to the value of the useful signal. With a negative useful component in the signal input to the driver I, the output of analog adder 9 produces negative pulses whose duration is also proportional to the amplitude of the signal. On fng. 2 shows the voltage at the output of the imager, 1 - and the voltage at the output of the converter 4 voltage to frequency - b, the voltage at the output of element 7 EQUIVALENCE - to the voltage at the direct output of the trigger 2 - g, voltage to the inverse output of the trigger 2 - d; the voltage at the output of the element 6-; the voltage at the output of the element 5 - f apr at the output of the inverter 8 - 3; apr at the output of the analog summer 9 - i. The introduction of additional elements into the demodulator allows the dynamic range to be expanded at the expense of reducing the minimum signal extracted with a predetermined signal-to-noise ratio at the output of the demodulator, due to the fact that at a zero useful component contained in the input frequency-modulated signal, the input of the filter is a signal equal to zero, and when the useful component is close to zero, a pulse sequence arrives at the input of the filter, with a duty cycle of more than two. In this case, the amplitude of the first harmonic is much less than the maximum, and hence the noise at the output of the demodulator is much less than the noise level at the output of the known, demodulator. The reduction in the first harmonic level is especially important when the ratio of the carrier frequency to the frequency of the modulating signal is close to unity, since in this case difficulties arise in extracting the useful signal and the requirements for the filter are increased. Claims of the invention A signal demodulator containing an input driver, the input of which is connected to the input width, and the output is connected to the first trigger input, a filter, voltage to frequency converter, the KOTOpoto input is connected to the filter input and the output is connected to the second trigger input, differing from that, in order to expand the dynamic range, the first n second elements I, the element EQUIVALENCE, the inverter, the analog adder are entered into it, the inputs of the element EQUIVALENCE are connected to the trigger inputs, and the output is connected to the first inputs of the first and second elements And, the second inputs of which are connected respectively to the first and second outputs of the trigger, the output of the first element And connected to the first input of the analog adder, the second input of which through the inverter is connected to the output of the second element And, the output of the analog adder is connected to the input of the filter, the output of which is connected to the output bus. Sources of information taken into account in the examination 1. USSR author's certificate number 427462, cl. H 03 K 9/06, 1972. 2. For Japan, 52-29903, cl. H 03 K 7/06, 9/06, - J977.